On specificity of 2nd generation TSH receptor autoantibody measurements.
BACKGROUND
TSH receptor (TSHR) antibodies (TRAb) are the hallmark in the serological diagnosis of Graves' disease (autoimmune hyperthyroidism). Irrespective of receptor origin second generation TRAb assays have been shown to be more sensitive than original first generation assays. The specificity of both assay generations is claimed to be close to 100% for discriminating healthy individuals from Graves' disease patients. However, there are a small number of Hashimoto's thyroiditis (autoimmune hypothyroidism) patients demonstrating detectable TRAb.


METHODS
One hundred and sixty-six Hashimoto's thyroiditis patients and 72 with Graves' disease were tested in second generation assays employing porcine and recombinant human TSHR. Receiver operating characteristics (ROC) were calculated for comparison.


RESULTS
Using a threshold of 1.5 IU/L for both assays, 7 out of 166 Hashimoto's patients demonstrated positive TRAb in the human TSHR assay whereas only 1 patient was measured positive in the porcine TSHR assay (specificity: 95.8% and 99.4%, respectively). Seventy-one out of 72 Graves' disease patients were positive in the human TSHR assay whereas 70 showed positive results in the porcine TSHR assay (sensitivity: 98.6% and 97.2%, respectively; ROC p = 0.16).


CONCLUSIONS
In this study, two commercial second generation TRAb assays with differing TSHR have been compared regarding the specificity in Hashimoto's thyroiditis patients. The slightly higher sensitivity of the human TSHR assay is obtained at the expense of a lower specificity. The impact of the different specificities should be considered due to the differing type of therapy for both patient groups.
Zöphel
Klaus
K
Department of Nuclear Medicine, Carl Gustav Carus Medical School, University of Technology Dresden, Germany. klaus.zoephel@uniklinikum-dresden.de
Grüning
Thomas
T
Roggenbuck
Dirk
D
Wunderlich
Gerd
G
Kotzerke
Joerg
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006111:Graves Disease / Q000097:blood*; D050031:Hashimoto Disease / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011989:Receptors, Thyrotropin / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D012680:Sensitivity and Specificity; D013552:Swine
D001323:Autoantibodies; D011989:Receptors, Thyrotropin; D011994:Recombinant Proteins